Denny Duquette is a longtime heart patient of Dr. Preston Burke who needed a life-saving transplant. He and Izzie fall in love while he is at the hospital, and this bond leads Izzie to make a decision that could jeopardize her medical career. Denny is afraid of hospitals and can't sleep when he's in them. He also develops friendly relationships with most of the doctors, with the notable exception of Alex Karev, who is jealous of Izzie's feelings toward Denny. Denny's father told Izzie she was nothing like the women Denny usually dated and they fell in love and Denny made a lasting impression on Seattle Grace.